I sent out my first invites for Google+ last night. I posted about it and expected I'd invite a few more people in the morning, only to wake up and find the invite option was gone. According to Vic Gundotra invites were switched off due to "insane demand." Hopefully we'll see them on again soon.
So far, I'm quite happy with Google+. The privacy model makes sharing scope much more prominent than other social networking sites (why name names?). It's easy to tell who a post will be shared with and I can change that scope as I see fit using "circles" (a.k.a., groups, lists, etc.). +1 is already implemented, of course. I'm looking forward to trying a "hangout" group video chat once a few more of my friends are on board.